Revert "Allow tab key to be used for shortcuts"

This reverts commit cafb888361eba08297dd88b18dc71f4d418525c0.

Fixes #34405.
Reopens #8799, #24064.

scene/main/viewport.cpp

@@ -2407,12 +2407,12 @@ void Viewport::_gui_input_event(Ref<InputEvent> p_event) {
 
 			Input *input = Input::get_singleton();
 
-			if (!mods && p_event->is_action_pressed("ui_focus_next") && input->is_action_just_pressed("ui_focus_next")) {
+			if (p_event->is_action_pressed("ui_focus_next") && input->is_action_just_pressed("ui_focus_next")) {
 
 				next = from->find_next_valid_focus();
 			}
 
-			if (!mods && p_event->is_action_pressed("ui_focus_prev") && input->is_action_just_pressed("ui_focus_prev")) {
+			if (p_event->is_action_pressed("ui_focus_prev") && input->is_action_just_pressed("ui_focus_prev")) {
 
 				next = from->find_prev_valid_focus();
 			}